2019 ASHS Annual Conference

Sweet cherries are a high value crop that brings high returns to growers. Pitting is a condition that affects all cherry cultivars, to varying degrees, and reduces the marketability of this high-value crop. Lessening the degree of pitting increases the aesthetic appearance of fruits making more available for marketing. The goal of our research was to understand the underlying mechanisms leading to pit formation and compare sensitive and resistant cultivars. Pit formation emanates from impacts that occur on the tree and after harvest. Understanding the molecular and physiological processes leading to pit formation enables development of knowledge-based treatments to reduce pitting and provide molecular and phenotypic tools for future breeding of low-pitting cultivars. To elucidate the mechanisms behind pitting, a three year study of sweet cherries was conducted in collaboration with the Agricultural Research Organization at the Volcani Center. Six different varieties were included in the project. Two varieties were considered resistant to pitting (Rainier and Bing) while the other four were deemed sensitive (Brooks, Chelan, Coral, and Lapins). For each of the six varieties, cherries were subjected to a controlled impact to induce pitting. The progress of the induced pit development was recorded over the span of one month with fruit stored at 0°C. Cherries from each variety were also collected from local packing houses and observed for a month during storage at 0°C to document development of natural pitting. Pitting severity was judged using a predetermined 1-5 scale. Total and apoplastic calcium content were measured in all varieties at 0 and 3 days after harvest. Additional cherry fruit were dipped in 1% calcium chloride prior to impact to induce pitting. Activity of several enzymes involved in oxidative stress were evaluated in one resistant variety (Bing) and one susceptible variety (Brooks). Enzyme activity was measured at 0, 1, and 7 days after harvest on one group of fruit that was impacted and a separate group that was not impacted. All calcium and enzyme assessments were evaluated in conjunction with pitting to relate pitting severity to these factors.